(a) Field of the Invention
The present invention relates to a device and method for determining current imbalance of a DC-DC converter. More particularly, the present invention relates to a device and method for determining current imbalance a DC-DC converter by measuring a voltage drop of each connecting portion to simply detect a saturation condition after supplying DC power to an output side without operating the DC-DC converter.
(b) Description of the Related Art
Generally, a DC-DC converter boosts or drops a DC voltage for subsequent use in a variety of areas. The DC-DC converter includes a power module that transforms an input DC voltage to AC voltage in a first side of a transformer, and a rectifying portion that rectifies the transformed AC voltage to a DC voltage in a second side of the transformer.
The power module includes two pairs of transistors as switching elements, wherein DC voltage is transformed to a periodic AC signal according to an operating order of the transistors.
FIG. 6 shows a circuit of a conventional insulation type of full-bridge converter in which a first side is a full bridge and a second is a center tap, and which is suitable for a DC-DC converter for a vehicle that requires high capacity, small size, and lightness in weight.
However, the biggest drawback of such a full-bridge type of converter is saturation of a transformer core. In particular, when the transformer becomes saturated, it looses its magnetic characteristic which can damage the converter.
There may be two potential causes of the transformer saturation. A first case occurs when an average voltage of a transformer input voltage is not 0, and a second case occurs when a second side impedance of a transformer does not coincide.
FIG. 7 shows a B-H curve of a transformer core, wherein (a) of FIG. 7 shows that the transformer core does not exceed a saturation area and is operated within a normal range, and (b) and (c) of FIG. 7 show that a transformer is saturated outside of the normal range because an operating area of the transformer is biased toward one side.
FIG. 8 further shows a transformer first side current (Ip) waveform in a normal case. As shown in FIG. 8, the current waveform has an up/down symmetrical structure such that it is not biased toward one side. Conversely, FIG. 9 shows a current waveform of a transformer in a case in which saturation occurs and the current leans upward, which is demonstrated by the sharp rise in the current waveform. This denotes that the transformer is saturated and does not function as a magnetic member in this area.
However, this method for determining the imbalance of the converter through use of the waveform as described above is not objective, and therefore it is not a suitable or reliable method for determining whether the converter is operating in a normal range or whether there is saturation.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.